In the coming year (1975) we will continue our studies that identify the influence of hypertonic mannitol on coronary blood flow, ventricular performance, and the extent of myocardial injury in ischemic cardiac muscle. Specifically, we plan to conduct experiments to 1) determine whether mannitol reduces infarct size in anesthetized dogs using standardized histological techniques of measuring infarct size, 2) determine whether hypoxic and/or acidotic cardiac muscle retains fluid abnormally and if it does if mannitol alters that, 3) whether mannitol exerts an inotropic effect and an effect on coronary blood flow in acidotic (lactic and hypercarbic acidosis) cardiac muscle, and 4) determine the relative safety with which mannitol can be administered chronically (organ function and organ histology testing).